Device and process for performing chemical analyses



June 20, 1939.

A. c. \SEATON 2,162,978

DEVICE AND PROCESS FOR PERFORMING CHEMICAL ANALYSES Filed Oct. 9, 1937MIMI! IN V ENTOR. 171 @527" 655/274, BY

ATTORNEYS.

Patented June 20, 1939 UNITED STATES PATENT OFFICE Albert C. Seaton,Indianapolis, Ind.

Application October 9,

4 Claims.

My invention relates to chemical analyses of the type in which thepresence of a suspected ingredient in a liquid is indicated by a colorchange when the liquid is heated, usually after the addition of one ormore reagents. The well known procedure of testing urine for thepresence of sugar by the use of Fehlings solution is an example of suchanalyses.

The making of analyses of this type has heretofore been restricted tosituations in which there is available a certain amount of equipment inthe way of reaction vessels such as test tubes, reagent bottles, and aBunsen burner or other heating means, and the field of use of suchprocedure is therefore limited. Moreover, such tests require that theperson conducting them be capable of interpreting the results obtained.This method of testing is open to the further objection that certainconditions, such for example as cloudiness of the liquid being tested,prevent or delay the obtaim'ng of satisfactory results.

It is the object of my invention to improve the test procedure describedabove to eliminate the necessity for extensive equipment or anysubstantial degree or skill on the part of the operator. Morespecifically, it is my object to provide a device and a procedure whichwill enable accurate results, both quantitative and qualitative, to beobtained and automatically recorded in permanent form. Another object ofmy invention is to provide a small and light-weight test device whichcan easily be carried on the person or transported through the mails.Still another object of my invention is to eliminate the effect of somefactors which, in the conventional procedure, make difficult or delaythe obtaining of accurate test results.

In carrying out my invention, the procedure I employ is to impregnatepaper or other suitable material with the reagent or reagents to be usedin the test. This paper or other material, after being dried, is dipped.into the liquid to be tested and, after waiting for a short interval toinsure solution of the solid reagent or reagents with which theabsorbent material has been impregnated, a controlled quantity of heatis applied to a localized area of the paper to cause the test reaction.The presence of thesuspected ingredient will then be indicated by theformation of a spot of color within the heated area of the paper, andthe size of this spot and its depth of color will constitute areasonably accurate quantitative indication of the amount of suspectedmaterial present in the liquid tested.

In its preferred form, the test device is made of 1937, Serial No.168,252

two strips of metal of relatively high heat conductivity, and theabsorbent paper or other material, impregnatedwith such reagents as thetest requires, is clamped in a definite location between them andarranged to extend laterally therefrom. At a point remote from thelocation of the paper, the metal strips are formed to provide a supportfor a quantity of combustible material. When the end of the laterallyprojecting paper is dipped into the liquid to be tested such liquid willpermeate all parts of the paper thoroughly as the result of capillaryattraction and will dissolve any reagents with which the paper wasimpregnated. Thereafter, if the combustible material is ignited, heatresulting from its burning will be conducted through the metal strips tothat portion of the paper which is clamped between the strips and willraise the liquid therein to the reaction temperature. Upon completion ofthe test, the strips of metal are separated and the paper removed tomake visible that portion to which heat has been applied.

The accompanying drawing illustrates my invention: Fig. 1 is a sideelevation of a preferred form of the test device; Fig. 2- is a plan viewof the finished device; Fig. 3 is also a plan View, but illustrates thetwo metal strips separated for the insertion of the paper and thecombustible material; Fig. 4 is a section on the line 4-4 of Fig. 2;Fig. 5 is a transverse section on the line 5-5 of Fig. 4; Fig. 6 is anisometric view of the device with a portion thereof broken away; andFig. 7 is a plan view of one of the pap-er strips.

In the particular form illustrated in the drawing, the device embodies asingle piece of square wire bent upon itself to form two co -extensivelegs l0 and H. The wire employed should be of copper or of some othermaterial having high heat conductivity. At an intermediate point, eachof the legs Ill and H is flattened to produce an enlargement l2, and thecenter portion of each enlargement is displaced inwardly in the form ofa circular boss l3. The extreme ends of the legs Hi and II are bentdownwardly and then rearwardly beneath the bodies of the legs, and suchrearwardly extending portions are shaped to provide conjointly anupwardly opening cup [4.

If two or more reagents are used in the test, and especially if they areof such nature that it is necessary to prevent any possibility of areaction between them before making the test, I may embody in the testdevice a plurality of strips of paper or other suitable materialseparately impregnated with the several reagents. Thus, in a deviceintended for use in testing urine for sugar content, I may employ twostrips of paper, one impregnated with copper sulphate and the other withsodium carbonate, the sodium carbonate being carried by a strip ofabsorbent paper or other suitable material I having a width slightlygreater than the diameter of the boss l3 and of a length to projectdownwardly for a considerable distance below the cup I4, and the coppersulphate being carried by a second strip I6 which has approximatelytwice the length of the strip I5 and the same or slightly greater width,and which is provided at its ends with openings I1 of a diameter toreceive the bosses I3. If a single reagent or none at all is requiredfor the test, the strip I6 may be eliminated.

In assembling the device, the two legs I0 and I I are separated asindicated in Fig. 3, the strip I6 is doubled over the strip I5 andinserted between the flattened portions I2 on the two legs I0 and II,with the holes I! placed over the respective bosses I3, and the upperend of the strip I5 disposed between the bosses the surfaces of whichmay be roughened to obtain a more intimate contact with and a firmerclamping of the paper between them. While the legs I6 and II are stillseparated, a pellet 26 of combustible material is inserted into the twohalves of the cup I4.

When the two legs I0 and I I are returned to the normal positionillustrated in Fig. 2, the upper end of the strip I5 will be clampedbetween the two bosses I3, the ends of the strip I6 will be held inplace by engagement of the holes I! with the bosses I3, and the pellet20 of combustible material will be retained in position in the cup I4.Desirably the pellet 20 is so formed as to engage the lower surface ofthe legs l0 and II to prevent its displacement from the cup I4. Alterassembly, a sleeve 2| of some suitable heatinsulating material may beslipped over the ends of the legs I0 and II to hold them together and toprovide a handle by which the device may be held while the test is beingconducted.

In making the test, the device held with the strips I5 and I6 extendingdownwardly from it as indicated in Fig. 1 is dipped into the liquid tobe tested and then removed. The looped strip I6 will retain sufiicientliquid to dissolve any reagent or reagents in the strips I 5 and I6.After waiting a suitable interval to insure the saturation of thatportion of the strip I6 clamped between the bosses I3 with liquidbearing the dissolved reagents, the pellet 20 is ignited. As it burns,heat is transferred to the outer ends of the legs I 0 and II and isconducted rearwardly to the bosses I3 where itis transmitted to theupper end of the strip I6 between the bosses and raises the liquidtherein to its boiling point. When the pellet 20 has been entirelyconsumed, the handle 2| may be removed, the legs I0 and II separated,and the absorbent strips I5 and I6 withdrawn.

In a device adapted for testing urine for sugar and embodying stripsI5I6 carrying the reagents above noted, the presence of sugar will beindicated by a reddish or reddish brown spot of copper oxide on thatportion of the strip I6 which was clamped between the bosses I3, and thesize of this spot will be indicative of the proportionate amount ofsugar present. To facilitate reading the size of the copper oxide spot,the upper end of the strip I5 may have printed upon it a grid or systemof co-ordinates, as indicated in Fig. 4.

To control the quantity of reagents present in the strips I5 and I6,those strips may be respectively immersed in solutions of the reagentsof a strength suiiicient to leave the proper quantity of reagents in thestrips after they are dried. The strips I5 and I6 are made of materialthrough which liquids can readily pass by capillary attraction; so thatcomplete immersion of the strips in liquid will not be necessary tosecure uniform saturation. I have found paper of the grade customarilyused for filter paper to serve the purpose excellently.

The material employed for the pellet 20 may vary widely. For bestresults, the material should 'be one which does not melt or disintegrateas it burns; as otherwise some of it might be lost and an inadequatequantity of heat obtained. I have found hexamethylene-tetramine, finelypowdered and compressed into a tablet of desired dimensions, to be verysuitable.

A device which I have employed with satisfactory results in testingurine for its sugar content has embodied strips I 5 and I6 of filterpaper, the strip I5 being approximately of an inch in Width and otherdimensions of the device being in about the proportions indicated in thedrawing. The strips I5 and I6 were impregnated with the reagents in themanner indicated above, the strip I5 containing approximately 7 mg. ofsodium carbonate and the strip I6 containing approximately 20 mg. ofcupric sulphate. The pellet 26 was a compressed tablet ofhexamethylenetetramine and weighed about 125 mg.

By testing solutions of known sugar content with my device, I have foundthat a rather definite relation exists between the size of the spot ofcopper oxide produced on the strip I5 and the proportionate quantity ofsugar present in the solution. Quantitative results obtained in this wayare considerably more accurate than estimates based on the results ofvisual observation of test-tube reactions.

My test device, being small and compact, is readily transportable andtherefore may be made more easily available than the equipment necessaryin other test procedures. No skill is necessary in conducting the test,as no measurements are required. The results of the test are permanentlyand automatically recorded by the production of the copper oxide spot onthe strip I5; thus making it unnecessary for the one reading the resultsof the test to conduct it. All factors which might affect the results ofthe test are readily controllable, the amount of each reagent presentbeing regulated by the strength of the solution with which each strip ofabsorbent material is saturated, and the quantity of heat or thereaction temperature being controlled by the size and nature of thepellet 20, by its distance from the bosses I3, and by thecross-sectional area of the wires through which the heat is conducted tothe absorbent material.

I claim as my invention:

1. A method of testing urine for the presence of sugar, which comprisespartially immersing in the liquid juxtaposed strips of absorbentmaterial respectively impregnated with cupric sulphate and an alkalinematerial, permitting the liquid to spread therethrough by capillaryattraction, and applying heat to a portion of one of said strips whichwas not immersed.

2. A method of testing urine for the presence of sugar, which comprisespartially immersing in the liquid juxtaposed strips of absorbentmaterial respectively impregnated with cupric sulphate and an alkalinematerial, permitting the liquid to spread therethrough by capillaryattraction, and conducting heat through a member of heat-conductingmaterial to a point on such member in contact with a portion of one ofsaid strips which was not immersed.

3. A device for use in performing chemical analyses of liquids,comprising two parallel metallic wires having at an intermediate pointopposed flattened portions adapted to grip between them a strip ofabsorbent material projecting laterally from the wires, a handle ofheat-insulating material embracing said Wires at one end, and means atthe opposite ends of said wires for supporting a pellet of combustiblematerial in heat-exchanging relation with the Wires.

4. A device for use in performing chemical analyses of liquidscomprising an elongated metallic body, means intermediate the length ofsaid body for holding in contact therewith a strip of absorbent materialprojecting laterally from v the body, a handle of heat-insulatingmaterial at one end of the body, and means at the other end.

of the body for holding a pellet of combustible 10 material inheat-exchanging relation therewith.

ALBERT C. SEATON.

